In the recycling industry, one substantial problem is to open bags containing recyclable materials. This problem arises because many communities require residents to place all their recyclables in a single plastic or heavy duty paper bag. These bags are then collected and delivered to a recycling center where the bags are opened, and the various recyclable materials are sorted.
Reliably and safely opening the bags is a difficult task, and many recycling centers have been able to accomplish this task only with excessive manual labor. The difficulty arises in part because the bags must be made strong enough to withstand the rough handling they are likely to encounter between the time residents fill the bags and the time they arrive at the recycling center. The toughness which allows the bags to arrive intact also makes them hard to open.
A second problem any bag opener must address is worker safety. The bags of recyclables may not only contain relatively benign items such as empty plastic beverage containers, but they may also contain more dangerous items such as propane tanks and aerosol cans of various types. These containers and their contents may pose significant hazards to those who must work sorting the contents of bags containing recyclable materials. An automated bag opener should be able to open bags while breaking as few of the contents as possible, and do this at a speed that makes the financial investment in bag opening machinery economical compared to the manual alternative.
Further the bags may contain materials that could easily damage any equipment used to open the bags. Such materials include large pieces of lumber, e.g., odd bits of 4".times.4", as well as glass. Glass poses a special problem since when it is broken, it is difficult or impossible to sort into the appropriate recycling category, and broken glass is exceedingly abrasive and therefore causes excessive wear on any machinery it contacts. Moreover, some items such as bundles of newspapers found in bags of refuse may tend to jam a bag opening machine. A machine that is used to open bags must be able to handle safely all of these materials with a minimum of down time for repairs or unjamming of the machine.
Equipment available before now has addressed some of these problems but has not been entirely successful in addressing the wear problem caused by abrasive materials, and worker safety and efficiency can always be improved. One prior art device for opening bags is that illustrated in U.S. Pat. No. 4,555,212. It includes a feed screw positioned in a tube. The tube has been partially cut away to form an inlet area at one end of the screw and a discharge area at the opposite end of the screw. The inlet area has wings that form a trough to direct bags toward the feed screw. Two portions of the tube between the inlet and discharge areas remain intact. In these two portions the tube completely surrounds the feed screw to form restrictions where the bags are severed. An expansion chamber is located between the two restrictions. In the expansion chamber the recyclables and any unopened bags are tumbled before going through the second, bag-rupturing restriction. After the feed screw advances the bags and their contents through the second restriction, they move to the discharge area where they spill onto a conveyor belt for further sorting.
The device described has proven effective, but it is also subject to premature wear, and it may have difficulty dealing with materials that are not easy to shear. The expansion chamber is open and might present a hazard. Moreover the feed rate of the screw must sometimes be slowed down because material accumulates in the expansion chamber.